Annealing furnace



Feb. 2, 1943.

E. l. HUFF ANNEALING FURNACE Filed Dec. 1, 1941 3 Sheets-Sheet lINVENTOR ATTORN EYS Feb. 2, 1943. HUFF' 2,309,700

ANNEALING FURNACE '7 Filed Dec. 1, 1941' 3 Sheets-Sheet 2 2 III] lk-llll,

jig. JZI.

INVIENTOR ATTORNEYS Patented Feb. 2, 1943 ANNEALING FURNACE Edward 1.Hail, Nutley, N. J., assignor to Huff Equipment Company, a corporationof Pennsylvania Application December 1, 1941, Serial No. 421,150

5 Claims.

This invention relates to annealing furnaces of muflie type, fired byflame, in which the muflie chamber is of annular form in horizontalsection, and adapted by shape to the annealing of such articles ascoiled steel strip and coiled wire. Furnaces so characterized are shownand described in Letters Patent granted on my application, No.2,146,432, February 7, 1939, and. No. 2,250,868, July 29, 1941; and alsoin a pending application, filed by me November 25, 1941; Serial No.420,393.

In the furnaces of the patents named, the flame enters the furnacechamber at the base and through the walls of the hood, and flowsupwardly over the outer wall of the annular mufile and, passing over thetop, descends through the central columnar space defined by the innerwall of the muffle. According to my present invention, as also in theapplication named, the flame enters the furnace chamber at the bottom ofthe columnar space defined by the inner wall of the mufiie, and flowsthence upwardly, over the top of the mufile and downwardly over theouter wall of the mufile to exit at the base of the hood.

This new arrangement is not a mere reversal in organization, for inconsequence of reversal new utility is realized; and, furthermore, inconsequence of such reversal, it has been possible to make particularstructural changes, with the effect that the annealing operation isimproved and rendered more efiicient.

In the accompanying drawings Fig. I is a view in vertical and axialsection of an annealing furnace in which my invention is embodied; Fig.II is a fragmentary view to larger scale of a portion of the furnace asseen in Fig. 1; Figs. III and IV are views in horizontal section, on theplanes indicated, respectively, at III-III and IVIV, Fig. I; Fig. V is afragmentary view (on reduced scale) in horizontal section, on the planeindicated at VV, Fig. II; and Fig. VI is a fragmentary view showing invertical and axial section the lower portion of a furnace in which areembodied specific structural features, other than those of Figs. I-V.

Referring, first, to the furnace as shown in Figs. I-V, it is, as hasbeen said, an annealing furnace of mufile type, in which the mulile isof annular shape. Upon a suitable floor plate I is placed a hearth block2; the hearth block carries the base plate 3 of the muflle; and uponthis base plate the muiile 4 is removably borne. The hood 5 is removablyborne by the floor plate I,

' 9 and III by air under pressure.

and when in place the hood at its base immediately surrounds the hearthblock 2.

The hearth block 2 of refractory material is centrally perforate; theorifice is circular and is of substantially equal diameter with thecolumnar space defined by the inner wall of the muflle. In the centralperforation of the hearth block 2 is set the burner block 6 of a burnerI. The burner block too is formed of refractory material. The burner maybe adapted to burn any suitable fuel-gas, oil, or finely divided coal.As here shown, it is an oil burner, fed through a pipe 8 by oil underpressure, and through pipes Through the burner block 6 the burnerprojects flame upwardly from below into the columnar space defined'bythe inner wall of the mulfle which columnar space is part of the furnacechamber beneath hood 5.

The base plate 3 is formed of metal-ordinarily, of cast-iron. It isessentially annular (since it forms part of the annular muflie) andconsists of a horizontally extending web II, radially arranged flanges33 that extend from the nether face of web II, co-axially arrangedcylindrical flanges I2, I3, I4, and I5 that extend from the upper faceof web II, and radially arranged flanges I6 that extend from the upperface of web II and between the cylindrical flanges I3 and I4. The radialflanges 33 immediately engage the upper face of the hearth block and,with the block below and the web II above, define passageways 25 beneaththe muflie, whose utility will presently be indicated. The pairs ofcylindrical flanges I2, I3 and I6, I5 form with the web II troughs intowhich in the assembly the inner and outer rims at the lower end of themovable muflle 4 extend and within which the muiiie is sealed by thefamiliar sand seal. The radial flanges I6 afford support for an annularplate II which is the stool-plate upon which the furnace charge rests.

The muffle is formed of heatconducting material, ordinarily of steel; itis, as has been said, of annular form and includes inner andoutersubstantially cylindrical side walls II, 42 that companion flange l3,and the flange IS in turn rises higher than the flanges I4 and ii, thatthe application of the muilie to the base plate may be facilitated.

The hood is formed essentially of refractory material it is of a generalform and arrangement already well known to the art. It is providedexternally wth rings l8 that engage stationary posts I! rising from thefloor plate, and by such engagement the hood is guided when beingapplied and removed. Within the hood walls flues 20 are formed. Ports 2|open to these flues from within and near the base of the hood. At theirupper ends these flues are freely open. They may vent to the open air,as here they are shown to do; or, manifestly, they may be brought intocommunication with a stack or other draftinducing apparatus.

Through the floor plate and base block tubes 22, 23 may extend, for thecirculation within the closed muflle of any desired gas (non-oxidizing,reducing, etc.) and tube 24 also may be similarly arranged, for theintroduction of a thermo-couple or other instrument for determiningconditions within the mums.

Operation is conducted in familiar manner. When hood and mufile havebeen removed the charge of material to be annealed is stacked upon thestool plate IT. The muflle 4 and the hood 5 are then successivelybrought to position. At the beginning, or as operation progresses, suchgas as may be desired for protection or for reaction is caused tocirculate through pipes 22, 23 and through the muflie chamber. Theburner I is lighted, or being already lit, is adjusted to afford a flameof desired size and character. The flame streams in the course indicatedby arrows in Fig. I, upward through the columnar space formed by theinner wall of the muille, over the top, and down over the outer wall ofthe muille, to the exit ports 2 I. have been completed and largequantities of heat generated by combustion will have been absorbed bythe muille walls. The products of combustion will escape through theflues 20 in the hood.

The passageways 25 formed by and between the flanges 33 that extend fromthe nether surface of the base plate H afford a by-pass, through which aportion of the stream of spent gases will return to mingle with thestream of burning gases that springs from the burner.

The heating operation properly controlled (as. may be, with the aid of athermo-couple) is performed in accordance with a known temperaturegradient; cooling may be accelerated by shutting oi the fuel and causingair at suitable temperature to enter through the burner block andcirculate through the furnace chamber; and when a proper degree oftemperature has been reached the furnace may be opened and the annealedcharge removed from it.

'The advantages of the structure as described, in which the stream offlame is upward through the columnar space within the ring-shaped muffleand downward over the exterior surface, over the usual arrangement, inwhich the flow of flame is upward over the exterior and downward throughthe central columnar space, are these: (1) The structure of the hood isnot complicated, and its manipulation in service is not embarrassed bythe presence of burners in that portion of the structure. (2) There ismore perfect dis tribution of heat circumferentially of the mufile thanis possible in case oil burners be arranged oircumferentlally and atintervals at the base of In this course combustion willconsequence offlow of spent gas from the base of the hood adjacent the ports 2| inwardthrough passageways 25 to the stream of burning gases that springs fromburner block 6, an equilibrium of pressure is established throughout thecourse of stream flow, with the consequence and eflect that localizedconcentration of heat is avoided, heat absorption by the muflle walls ismore evenly distributed and brought to maximum total value, and the lifeof the structure is prolonged.

Another and an alternative elaboration of structure, rendered possibleby the reorganization of the furnace and the arrangement of the burnerat the centre with stream flow upward through the centre of the muilleand downward over the outside, is illustrated in Fig. VI. In this casethe passageways 25 are not provided. Instead, the floor plate IN isprovided with central and peripheral troughs 26 and 21 adapted tocontain proper quantities of sealing liquid. Both troughs extenddownward below the level of the floor plate; the walls of the innertrough 26 rise above the level of the floor plate and between the burnerblock I06 and the hearth block I02; these two blocks in this case beingspaced apart sufficiently to allow such an intrusion of the trough. Thewalls of trough 21 are arranged wholly below the level of the floorplate. The muflle is so adapted that, when in place, it is borne by thefloor plate and yet its outer and its inner lower rims extend freewithin the two troughs 26 and 21. To accomplish this the inner wall ofthe muflle near its lower end is provided with a flange 28, by which itrests on the rim of trough 26 with its own rim extending free within thetrough 26, while the outer wall of the muille near the lower rim isspread outward in a flange-like plate 29 which in the assembly restsimmediately upon the floor plate NH, and at the outer edge of thisoutward spreading flange-like plate 29 the muille wall is continued in adownward prolongation 36 that extends free within trough 21. The hoodwhen applied rests immediately upon the flange 29 of the muille, whichflange in turn rests immediately upon the floor plate It. The twotroughs 26 and 21, arranged as they are beyond and beneath thesubstantially continuous horizontal wall of refractory material affordedby the burner block [06, the base block I02, and the hood 5, are remotefrom the region of intense heat. With such arrangement the seals forboth the inner and the outer rims of the mufile may be liquid seals, andin consequence the isolation of the material under treatment within themuille may be rendered more perfect. More complete protection of theliquid seals from access of heat may be afforded by cooling the floorplate by means of streams of liquid circulating in conduits 3| arrangedbeneath and conveniently formed upon its lower face.

I claim as my invention:

1. In an annealing furnace of muiiie type and having a muil'ie ofannular shape, such furnace including a base, a muifle, and a hood, themuifle and the hood being severally applicable to and removable from thebase and when applied forming between themselves a furnace chamber, theinvention herein described which consists in means for introducing flameto the furnace chamber at the base of the columnar space defined by theinner wall of the annular mufile,

and flues for the products of combustion opening from the furnacechamber through the hood and at the base thereof.

2. The structure defined in claim 1, having the additional provision ofa pressure-equalizing passageway leading from the outer basal portion ofthe furnace chamber to the inner basal portion thereof.

3. The structure defined in claim 1, having the additional provisionthat the base is provided with inner and outer concentric sealingtroughs in which the inner and outer lower rims of the mufile are borne,and pressure-equalizing passageways arranged beneath said sealingtroughs and leading radially inward from the outer basal portion of thefurnace chamber to the inner basal portion thereof.

4. The structure of claim 1, the base including a floor plate with innerand outer concentrically arranged troughs for sealing liquid extendingbelow the level of the floor plate and opening upwardly through thefloor plate, the muflle at its lower end being adapted, when applied, torest upon the floor plate, the muflle being provided with rims that,when the muflle is applied, enter the said troughs, and, so entering,are adapted to be submerged in liquid contained therein.

5. In an annealing furnace of muflle type and having a muflie of annularshape closed above and at its lower end terminating in inner and outerconcentric rims, the combination with a floor, a hearth block ofrefractory material and of annular shape borne by the floor, a burnerblock of refractory material centrally arranged within the hearth block,a trough adapted to contain sealing liquid formed in the floor, openingbetween hearth block and burner block, and extending below the floorlevel, a second trough adapted to contain sealing liquid formed in thefloor at an interval beyond the outer edge of the hearth block andextending below the floor level, the muflie provided adjacent its lowerinner and outer rims with supporting flanges, which flanges when themuflie is applied bear upon the floor and support the muflle with itsrims in sealing positions within the troughs, a hood of refractorymaterial adapted to rest by its rim upon the floor-engaging flange ofthe outer rim of the muflle. and a burner adapted to deliver a flamethrough the burner block, the burner block, the hearth block, and thehood forming at the floor a substantially continuous wall of refractory,protecting the bodies of liquid in the said troughs from access ininjurious quantity of heat from EDWARD I.

